Air-compressor



f Y 2 sheets-'sheet 2. W. T. vPORSTBR.

AIR COMPRESSOR.

. (No Model.)

Patented Jan. 17, 1.888.l

entre STATES PATENT rrrcn.

VILLIAMT. FOBSTER, OF KANSAS CITY, MISSOURI.

AIR-COMPRESSOR SPECIFICATION forming part of Letters Patent No. 376,589, dated January 17, 1888.

Application filed August 5, 1856.

i ence indicate like parts, Figure 1 is a sectional elevation of my improved compressor, showing the piston at the bottom of cylinder on the downward stroke and in dotted lines at the top oi' the cylinder, after having pushed the head orexhaust-vaive outward to allow the compressed air to pass from the cylinder to the reservoir. Fig. 2 isa sectional, plane view through the auxiliary device at the bottom of` the compressor. Fig. 3 is a modified construetion of the auxiliary at the bottom of the compressor.

lhe'compressor which is described in this specification is au improvement on or modiication of the air-compressor invented by me,

and for which I applied for Letters Patent on the 21st day of Oct-ober, 1885, which application was allowed May 1,1886, and is numbered 180,548; and the improvements or modifica tions consist in having a single exhaust-valve or sliding head for allowing the compressed air to escape atfthe top of the cylinder, and an auxiliary device for throwing compressed air into the cylin'derat the bottom of the latter, and a new arrangement of several ports by which a more perfect result is secured.

My improved compressor consists, essentially, of an air-cylinder containing a piston providedwith a movable head adapted to slide outward when the air within has reached the required degree of compression and uncover the port by which the compressed air escapes into the reservoir, and connected therewith a diaphragm or equalizer consisting of a hollow closed vessel, provided with a flexible side or end, which is attached to the movable head or exhaustvalve of the cylinder, and having its interior communicating with the reservoir, so

Serial No. M0127. (No model.)

as to be lled with compressed air, and also having at the bottom of the air-cylinder or end opposite the sliding head an inclosed chamber or space so arranged that when the piston returns from having compressed theairin the cylinder or is in its descent it compresses the air in the chamber and then allows this compressed air to pass into the cylinder, and thus increases the pressure of the air inv the latter before the piston commences its upward stroke or itself commences to compress the air in the aircylinder.

As shownin the drawings, and asIpropose to construct my improved compressor, A is the air cylinder,containing the pistonP,which is moved back and forth by the piston-rodp inthe usual manner. YAt one end of the cylinder, and fitting closely in the same, so as to render .it air-tight, is the movable head B, adapted to slide back and forth in the cylinder, and lprovided with the eircularinlet-valve C. In the walls of the cylinder, near the end and situated a little beyond the lower or inner face ofv the head B when the latter is in its place,

is the port d, extending around the cylinder, and provided with an out-let which communicates with the side or discharge pipe D, by which the compressed air passes into the reservoir.

The arrangement of the .port and head is such that when the latter is within the cylinder the sides of the head extend over or cover the port, as shown in the drawings, and thus prevent the air from passing out of the cylinder into the reservoir; but when the head is pushed out, as shown by the dotted lines in Fig. l, the side slides past the port and uncovers the same and allows the air to escape from the cylinder'. The movable head B thus forms the exhaust-valve of the compressor and controls the passage of the compressed air. As the port d is placed but a short distance from the inner face of the head or valve B when the latter is within the cylinder,the motion ofthe valve required to slide past or open the port 'is very slight.

IOO

next to the head B flexible or capable of expansion and depression. This fiexible side of the equalizer is formed by a circular series of detached steel plates, B, and a central movable disk, T, which is arranged to slide back and forth in an opening in the lower part of the frame M, as will be understood from Fig. 1. The outer ends, r, of the plates rest loosely on bearings m in the frame M, and the inner ends, i", rest on the disk T. The plates are thus held in such a manner that their inner ends can freely move out and in with the movable disk T. The back or inner side of this disk T is secured to the center of a sheet of rubber, O, or other suitable elastic material, which extends back of the plates R, and is tightly secured to the equalizer by being clamped between the two parts of the frame M. The rubber sheet thus incloses the equalizer at this flexible or movable side and renders it air-tight.

At the outer edge of the circular disk T,and immediately under the plates It, is a projecting rim, t, which is so constructed and arranged that when the disk is pushed or moved inward a certain distance the projection t will strike or come in contact with the outer surface of the plates, and thus change the fulcrum or movable point of bearing on the latter from the inner end, 1", to a point nearer the outer end, 1', and thereby decrease the length of the plates between the points of support, and so increase the resisting power or force of the plates. These plates B, which are preferably made of steel, so as to be capable of resisting great pressure, are constructed of such proportions and the projection t is so located and arranged that when the latter comes in contact with the plates and presses them inward the plates exert a resistance equal to or a little greater than the full pressure of the piston in the air-cylinder in compressing the air and pushing out the exhaust-valve. The central disk, T, and hence the flexible side of the equalizer, is connected by means of the post S with the outer face or side of the movable head or exhaust-valve B, and thus as the valve is pushed out the iiexible side of the equalizer is depressed, and as the latter expands or is forced out the valve slides back within the cylinder.

The interior of the equalizer L communicates by means of the tube U with the port (l, and the equalizer is therefore filled or charged with compressed air at the same degree as the air in the reservoir or as the compressed air in the air-cylinder.

The equalizer is constructed of such proportions with respect to the size and capacity of the air-cylinder that the pressure of the compressed air in the equalizer on the outer face of the exhaustvalve B is equal to the pressure of the compressed air in the cylinder on the inner face of the valve. This pressure on the outside of the valve holds it in place in the cylinder and prevents it moving until the air in the cylinder has been compressed to the required degree, when, as the pressure on both sides of the valve is equal, a slight increase of pressure in the cylinder forces the head or valve out and allows the compressed air to pass out of the port d. The other or opposite end of the cylinder is fitted with a plate, H, so as to be air-tight. This plate, which may be larger than the diameter of the cylinder A, in which the piston moves, is arranged to slide outward within the walls of the cylinder and form an inelosed chamber, A', below the piston when in its lowest position, after it has completed its descent. The plate is held in place when not pushed outward by springs h on rods h, attached to its outer edge, and has a valve, h, for admitting air into the chamber A.

In the walls of the cylinder, near the chamber A, are a series of holes or openings, K, and also a series of grooves or channels, I, Whose lower ends open into the chamber A', and which extend upward for a distance greater than the thickness of the piston-head I), as shown more clearly in Fig. 3. As the piston returns, after having compressed the air in the cylinder, and commences its descent, it forces the air below it out of the cylinder through the holes or openings K until the sides of the piston cover and thus close these holes, when the air below the piston is conned and compressed between the piston-head and the plate H. As the piston continuesitsdeseent the compressed air exceeds the force of the springs h', and the plate H is pushed outward to the end of the chamber A. The piston, continuing to compress the air in the chamber A, descends until its upper face, p', passes by the top of the channels I, when the compressed air in the chamber A at once escapes into the chamber A on the other side of the piston-head, and thus raises the pressure of the air with which the cylinder is filled, as will be understood from the drawings. The moment the compressed air passes out of the chamber A the plate H is drawn back by thc springs 7i', and as the piston commenees to ascend to compress the air in the cylinder A the air enters through the valve h and fills the chamber and cylinder behind the piston. The air in the cylinder A is thus partially compressed by the return movement of the piston, and the downward stroke of thelatter assists in raising the air to the required degree of pressure.

From the above description the operation of the compressor will be readily understood.

As the piston returns from having compressed the air in the cylinder A and descends toward the auxiliary chamber A the air, e11- tering through the Valve C in the head B, fills the cylinder A with atmospheric air. Thepiston, continuing to descend, compresses the air in the chamber A', as above described, and when it has reached its lowest point and is ready to ascend this compressed air passes into the cylinder A through the channels I and increases the pressure or density ofthe air in the cylinder A above the atmospheric air. The in- ICO creased pressure at once closes the valve C, and thus the air is coninedin the cylinder. The air in the cylinder A, as the piston commences to move toward the head B, is therefore raised above the pressure of `the atmospheric air, thereby greatlyincreasing the volume of air with only a slight increase of power to drive it.

As the piston advances toward the head the air inclosed between the surface of the piston and the inner surfaceV of the head is compressed until the desired degree of compression is obt-ained, or until the air in the cylinder is compressed to the same degree as that in the reservoirand in the equalizer communieating with the latter. At this moment, as the cylinder and equalizer both contain air at the same pressure, and as they are constructed of the proper proportion with respect to each other, the pressure on the under surface of the head or valve caused by the pressure of the air in front of the piston is equal to the press ure on the outer surface of the head or valve caused by the pressure of the air on the flexible side of the equalizer. The pressure on both sides of the head or valve is therefore the same, or the valve is balanced between the two equal pressures, and it follows that a' very Y slight additional-pressure either way will move the valve. As. the piston continues to advance, the extra or increased pressure on the underside of the head or valve forces it outward, and as the latter moves in the sides of the cylinder it uncovers or slides past the port d, and the compressed air Ypasses or escapes through the -side pipe, D,`into the reservoir.

As the head or valve slides or moves outward it depresses the flexible side of the equalizer connected with its outer face or surface until the rim t on the disk T comes in contact with the plates R, when, as the plates are so constructed and arranged as to exert a resistance greater than the pressure of the piston or outward force of the head, the depression of the side of the equalizer, and consequently the outward movement of the head or valve, is

checked, and thus the cylinder-head is preventedfrom sliding entirely out 0f the cylinder.

As will thus be seen, at the moment immediately preceding that at which the head or valve moves, and when the air in the cylinder has been compressed to the required degree,

the pressure on both surfaces of the head or valve is equal,`the pressure in the cylinder or on the underfsurface of the valve balancing that in the equalizer or on the outer surface of the valve. The force necessary, therefore, to move the valve is only that required to overcome the weight of the valve and the friction of the latter on the sides of the cylinder. As the valve is held in place in the cylinder by the pressure of the air in the equalizer on lits outer surface, and not by its own weight, it need not be Very heavy, and as it slides'but a little distance in order to uncover the port the force required to move the head or valve is very slight.

fcylinder head or valve In my improved compressor, therefore, the pressure of the piston necessary to move the exhaust-valve above that required to compress theair is very slight, and nearly all the power of the piston is applied in compressing the air. After the'compressed air has passed from the cylinder into the reservoir and the piston has commenced its return-stroke to the opposite head, the spring or resistance of the plates R, caused by the depression of the tlexible side of the equalizer by the movement of the cylinder-head and the force of the compressed air in the equalizer force this head back in the cylinder to its former position, thus closing the port and preventing the compressed air passing back into the cylinder. In order to insure a more perfect movement of the head back into the cylinder and closing of the port, I employ the device shown at E in the drawings. This consists of a movable cup, E, fitting in a recess in the inner face or surface of the and adapted to slide out and in in the same. This cup in its normal position projectsjust beyond the face of the head, as shown in Fig. I, being held there by springs e. On the outer surface of the cup is formed a depression or cavity, F, from which extend small channels e, terminating in the socket in which the springs e rest, and thus communicating with the space F' behind the cup E, as will be understood from the drawings.

Frein the space or chamber Fa channehf, extends through the head to the side of the latter, and communicates with the channel f,

formed in the wall ofthe cylinder. This channel f extends within the walls of the cylinder below the head, and terminates in the cylinder A at a point, f", which is so situated as to be immediately behind the piston-head P at the moment the head touches the cup Ein its ascent, as shown by the dotted linesin the drawings. An enlargement is formed at the upper end of the channelf, as shown at f', to accommodate the movement of the head and insure the communication of the channelsf and as the head slides out and in. y

'As will thus be seen from the above description and the drawings, the air in the chamber or space F and in the channels f and f is at the same degree of pressure as in the cylinder IOO IIO

in front of the piston, or between the piston 'Y and head B, as the former approaches thehead and compresses the air, and as the space F behind the cup E contains air at the same degree Vof pressure as the air in the cylinder in front of the cup, the cup is not pushed in as the piston continues to advance, but retains its position projecting from the head, as shown in the drawings.

After the piston has compressed the air in the cylinder to the required degree4 and has forced the head or exhaust-valve B outward, and thereby opened the port to allow the air to pass into the reservoir, it continues to adtil the air has escaped fromthe latterand the piston has come in contact with the surface of the head. As the cup E projects beyond the surface of the head the piston first strikes it and iucloses or shuts in the air contained in the depression or cavity F. At the moment at which the piston touches the cup E it slides by or uncovers the lower terminus,j", of the l channelf, and allows the latter to commuuicate with the cylinder A behind the piston, as show'n by dotted lines in Fig. l. As will be readily understood, the compressed air con- I filled in the cavity F and the compressed air I in the chamber F at once escape by means of the channelsfandf into the cylinder A behind the piston, and the cavity and chamber are filled with ordinary atmospheric air. As the air in the chamber F can now pass out of" the same through the channels, the cup E can be readily depressed or forced in as thc piston advances, and at the same time it is held closely against the latter by the springs c, and thus the air in the cavity F is shut in or confined by the piston-head. This air in the cavity F being ordinary atmospheric air, it follows, therefore, that when the piston has reached the head and is ready to return, the pressure of the air on the lower or inner surf'ace of the head is reduced by the amount of compressed air which has escaped from the depression in the eupE. The pressure on the inner surface of the head is thus less than that on the outer surface caused by the air in the equalizer. The cylinder-head is therefore l pressed down an d held closely against the su rface of the piston by the greater pressure in the equalizer, and as the piston returns the head slides back withit; hence the movement of" the head back into the cylinder is a very quick one and the port is immediately closed, and, moreover, as the head is held down close against the piston, there is no opportunity for the compressed air to pass back into the cylinder. The cup or device E furthermore I acts asa cushion t'or the piston to strike against, l and prevents the piston and cylinder-head l from being injured when they come in contact with each other.

By employing the cup E, constructed and operating as above described, and provided with the channels j' andf, the compressed air in the cavity F and in thechamber F" is returned into the cylinder A, and when used l with the air-compressor having an exhaustvalve at each end, as described in my application before mentioned, No. 180,548, filed October 2l, 1885, and allowed )lay l, 1886, the compressed air thus returned to the cylinder assists in filling the latter, and is not lost. Furthermore, with this construction of cup ll there are no valves required to retain the air in the cavity, the piston-head taking the place of the valve.

Any variety of inletvalvcs may be used to admit the air into the cylinder; but I prefer to employ the valves shown inthe drawings at C. These valves are circular and work in a valve-scat on the inner surface ofthe cylindcrl head. The valves consist of the V- shaped body C, made ofiron or other suitable metal, to which is secured the faceplate \V. Between the body G and plate XV is placed a rubber ring or cushion, V. The valve is held in the valve-seat by the stems C', arranged to allow the valve to play up and down in the seat, and provided with the spring c, to force the valve in when the pressure of the air in the cylinder against the face or plate XV is removed.

As the valve is forced in or opened by means of the spring c the air enters through the passage between the valves au d valve-seat and e11- ters the cylinder. As the piston moves toward the head ofthe cylinder and compresses the air within, it forces the valve against the valve-seat and closes the valve, thus preventing the passage of the air between the valve and seat. By means of the rubber cushion or packing V, as thc valve is pressed against its seat a more perfect and effective air-tight joint isinsured, and at the same time the blow or impact of the valve is lessened.

To insure a tightjoint between the cylinder heads or valves and the sides ofthe cylinder, rubber bands or packing is arranged in the sides of the valves, which is pressed closely against the sides ol" the cylinder by the compressed air introduced through the tubes X, communicating with the side pipe, l).

In iny improved comp rcssor require very little extra force or power to move'the valve, and as the valve slides but a little distance it is subject to but little wear and docs not rcquire to be frequent-ly refitted, as is the case with the valves now in use; and, moreover, as the valve is held in place bythe force of the compressed airin the diaphragm, which is the same as in the reservoir, the valve adjusts itself to any pressure required, always moving when the air in the cylinder is compressed to the degree desired or to the same degree as that in the reservoir.

lzy a suitable arrangement of the plates R and projections t the diaphragm can be made to resistany dcgreeof pressurerequired. This construction of' diaphragm may also bc used as a buffer wherever it is necessary to resist or overcome pressure.

Fig. illustrates a modified construction of the auxiliary chamber A at the end of the cylinder oppositie the sliding head or exhaustvalve. In this form of construction thc plate ll is firmly attached to the walls ofthe cylinder and does not slide back and forth in the same. The air is compressed in the chamber A by the piston and escapes by its own force through the channels I into thc chamber A, as described in the former construction.

W'hat I claim as new isl. In an air-compressor, the combination, with the air-cylinder having a single movable head adapted to act as the exhaust-valve ofthe compressor, of an equalizer provided with a flexible side connected with the inovablehead of the cylinder and adapted to contain air at I oe ISO

the same degree of pressure as is produced in the cylinder, substantially as and for the purposes set forth.

2. In an air-compressor, the combination of the cylinder A, having the 'port d, and provided With the single movable head B, having the valve C and cup E, with the equalizer L, communicating with the reservoir of compressed air, so as to contain air at the same degree of pressure as is produced in the air-cylinder, and provided with the flexible sheet O, plates It, and central disk,T, connected with the movable head B, and having the projecting rim t for acting upon the plates It, arranged and operating substantially as described, and for the purposes set forth. 3. In an air-scompressor, the equalizer L, capable of containing compressed air, having one side formed by the ilexible sheet O, and the disk T, attached to the center of such flexible sheet and provided with the projecting rim t for acting on the plates, and the elastic plates R, resting on the frame M and on the.

centradisk, T, substantially as and for the purposes set forth. l

4. In an air-compressor, the combination,.

with the cylinder, of a chamber situated at the end of the compressor beyond the piston when at its lowest position, and having an inletvalve for thepassage of air intothe chamber, and channels connecting the chamber with the cylinder, so constructed and arranged that the air is compressed in the chamber by the return-stroke of the piston, and is, then introduced into the cylinder through the channels in front of or on the other side of the piston, substantially as and for the purpose set forth.

5. In an air-compressor, the combination, With the air-cylinder, ofthe auxiliary cham- 40 ber A', having the sliding head or plate H,

held in place by the spring h on the rod h,

and provided withl the inlet-valve h, and having in the Walls of the cylinder the holes K for the escape of air and the channel I for the passage of the compressed air from the chamber A tothe cylinder, substantially as described, and for the purposes set forth.

6. In an air-compressor, the combination, with the cylinder-head B, of the movable cup E, itting and moving in a recess in such head,

and constructed with the cavity or .airspace F on its outer face, and provided with the channels e and springs e, and having the space or recess F between the cup and head communicating with the channel f in the head and the channelf in the Wall of the cylinder, so that the air confined in the cavity F can pass into the cylinder back of the piston-head,

substantial] y as and for the purposes set forth.

7. An air-compressor having the port d in the'lwalls ofthe cylinder, and the sliding head B, adapted to form the exhaust-valve, provided with the cup E and inlet-valve C, and the equalizer L, communicating with the reservoir of compressed air, for the purpose set forth, and provided with the flexible sheet O, elastic plates R, and central disk, T, connected with the sliding head B, and having the projecting rim t for acting on the elastic plates R, and the auxiliary chamber A', having the sliding plate H, held in place by the springs h or the rods h, and provided with the valve h and with the hole K and channels I, for the purpose described, all arranged and operating substantially as described, and for vthe purposes set forth.

Dated this 19th day of July, 1886.

WILLIAM T. FORSTER.

Witnesses:

ABBIE G. FoRs'rER, JULIET M. FoRsTnR. 

